Snap acting device and electric switch



INVENTOR. M Ii M BY M w M41 A TTO 2 NE Y5 A. L. RICHE SNAP-ACTING DEVICE'AND ELECTRIC SWITCH Filed Aug. 29, 1945 June 21, 1949.

Patented June 21, 1949 2,473,970 SNAP ACTING DEVICE AND ELECTRIC SWITCH Arthur L. Riche, Freeport, Ill., asslgnor Industrial Corporation, Wilmington, corporation of Delaware to First Del., a

Application August 29, 1946, Serial No. 693,738

9 Claims. (Cl. 200-76) This invention relates generally to an improved snap acting device and particularly to an improved snap acting electric switch mechanism. An object of this invention lies in the provision of an improved and simplified snap acting device having a movable member driven by a hammer blow from one preselected position to another;

specifically, one object is the provision of a snap acting electric switch in which the movable contact carrier is driven by a hammer blow from one switching position'to another.

Another object of this invention lies in the provision of a snap acting device in which a movable member is moved between preselected positions by the coaction of a pair of over-center snap spring systems, one of which is operable between spaced abutments on the movable member to apply a hammer blow to the latter to initiate its movement between its preselected positions, and a second over-center snap spring system for holding the movable member in either of its preselected positions; and a specific object is to adapt this spring system to an improved snap acting hammer blow electric switch construction.

Another objectis the provision of a self-returning snap acting device or electric switch incorporating the above stated features.

Other objects and advantages will become apparent from the following description in connection with the drawings in which- Figure 1 is a partially sectioned view of a selfreturning snap acting electric switch embodying the various features of the present invention, the parts being shown in their normal position;

Fig. 2 is a view similar to Figure 1v but showing the parts in their abnormal position;

Fig. 3 is a sectional view of Figure 1 taken on the line 33;

Fig. 4 is a partially exploded perspective view of the various elements of the switch, and

Fig. 5 is an enlarged perspective view of the switch showing the details of the movable contact.

Referring now more particularly to the embodiment shown in the drawing, the switch is mounted on a base I of suitable electrical insulating material. Stationary contacts 2, 3, 4, and 5 are mounted thereon by means of screws or bolts 6 which may be connected suitably to 2 wire conductors (not shown). Support memhers I and 8 are also mounted to the base I by means of bolts 9 and II, respectively. The upper support member I has mounted therein, parallel to the base I, a tubular guide I2 fastened as by soldering or a press fit in the guide bore I3. The

hollow guide I2 is formed with an internal bore I I. The lower support 8 is centrally bent away from and then back toward the base I to form an internal guiding slot I5. A movable contact carrier I 6 has an upper rod-like end extension I1 fitting pistonwise in the guide shaft bore I4 and is reciprocably guided therein. The opposite end of the movable member 16 is provided with a reduced extension I8 oi. substantially the same cross-section as the lower guide slot I5 and is reciprocably fitted therein for support. A movable shorting bar or'contact I9 having contacting end portions I9a and I9b and a reduced intermediate portion I is mounted crosswise to the axis of the carrier I6 within the opening 2 I. A locking strip 22 is mounted on the carrier by screw 23 and serves to maintain the movable contact I9 in place within the aperture 2| aiter assembly,'it being necessary to turn the movable contact I9 diagonally across opposed comers oi! the slot 2| to initially assemble it within the carrier, as will be obvious. It will be observed that the efiective height of the opening 2I after the locking strip 22 is in place is still somewhat greater than the thickness of the movable contact I9, this being one of the features of the present invention, which provides a lost motion engagement between the movable contact and the carrier for the purpose of facilitating the pivotal adjustment of the movable contact member upon the stationary contacts.

Mounted on the guide shaft I2, prior to assembly of the latter within the support bore I3, is a U-shaped operating member or yoke 24 and a bushing member 25 each bored to slide smoothly up and down on that portion of the guide shaft beneath the enlarged shoulder 26 which serves as a stop for the yoke and bushing in the upward or outward direction. An inverted cup-shaped operating button 21, usually of electrical insulating material, fits snugly around the reduced bushing surface 28 and bears at its bottom end on the bushing shoulder 29. Downward movement of the operating button and, therefore, of the yoke 24 and bushing 25 is limited by abutment of the inner closed end surface with the top surface 3! of the guide shaft i2. Biasing means, comprising the helical spring 32 fitting around the guide shaft I2 and bearing, respectively, on the support 1 and U-shaped yoke 26, urges the parts upward or outward to the normal position shown in Figure 1.

The ends 36 of the legs 33 of the U-shaped yoke 23 are reduced and turned inwardly for engagement with the ends of a coiled driving or hammer blow spring 35 which is maintained under compression due to the fact that the unstressed length of the spring 35 is greater than the distance between the bearing shoulders 38 on these inwardly turned yoke ends or fingers 3Q; thus, the coil spring 35 acts as an over-center snap spring. The intermediate portion of the spring 35 extends through an elongated slot 31 in the carrier I6 and in operation alternately bears against opposed spaced abutments 38 and 39 comprising the inner enc surfaces of the elongated slot 31.

Another aperture M in the carrier it has fitted or secured therein another coiled spring 42, this coil spring being usually somewhat smaller than spring 35 and having its ends fitted over the inwardly extending fingers 33 formed on the sta-- \I\ tionary supporting member 53 which is mounted don the base I by means of bolts 45. Spring 42 is likewise mounted under compression in the same manner as described in connection with spring 35 so that it, too, operates as an over-center snap spring, its function being to maintain the carrier in one or the other of two stable over-center switching positions depending on the normal or abnormal condition of the operating yoke 24.

In explaining the operation of the switch. it will be assumed first that the parts are in the normal position shown in Figure l and that the stationary contacts 3 and are electrically connected by the shorting bar or contact member H) which is maintained pressed into that position by the force exerted by one or both of the coiled sprin s 35 and 42: as will be pointed .out subsequent y, the employment of the holding spring 42 is not absolutelv essential to the operation of the present invention and in certain cases to be described may be dispensed with. To o erate the switch from the normal position the button 27 will be de ressed, thereby sliding the bushing 25 and operating yoke 26 downward (with respect to the switch as shown in the figures) in a direction to compress the biasing spring 32. This will also tend to straighten out the coil spring 35 by moving itsends downward and at the same time will increase the pressure of the movab e contact member I 9 on the stationary contacts above that wh ch may already be exerted by the holdine: spring 42. When the driving spring 35 is moved through'a certain position of maximum stress where its center portion is approximately ali ned with its pivoted end portions, its center portion will snap quickly upward through the lost motion space provided between the abutments 39 and 33 and will strike the latter at hi h velocity with a hammer blow, thereby driving the carrier it upward to the abnormal or Fig. 2 position, where stationary contacts 2 and 3 will be connected b the movable contact I 9. In moving upward in-this manner the carrier IE will move the holding spring 42 over-center, upward. where it will be effective to maintain the carrier I'B in abnormal position as long as the operating button'27 is maintained depressed to overcome the resistance of the biasing spring 32.

The reverse or release operation of the switch from the Fig. 2 position will be substantially the same, in reverse, as described above. The strength of the biasing spring 32 will be selected at a sufliciently high value that when the depressive force on the button 21 is released it will move the operating yoke 24 upwardly to overcome any resistance which may be set up by either or both of the springs 35 and 42. Thus, as the depressing force on the spring button is released, the yoke 24 will be moved upwardly or outwardly to move the ends of the spring 35 upwardly toward a position of maximum stress coinciding approximately with alignment of the center and ends of the spring; at the same time this upward movement will cause the spring 35 to exert a force on the carrier in a direction to press the movable contact i9 upward against the stationary contacts 2 and 3; this last mentioned force will be in addition to any force already exerted in that direction by the holding spring 42. When the spring 35 is moved upward through its position of maximum stress it will again snap quickly, downward this time, strikingthe carrier abutment 39 at high velocity imparting thereto a hammer blow which will be effective to drive the carrier downward once more to the normal or Figure 1 position. In moving downward in this manner, the carrier I6 will move the holding spring 42 over center where it will again be effective to maintain the carrier in its normal position.

The use of the holding spring 42 in combination with the driving spring 35 will usually be'preferable but not essential in each case inasmuch as the parts of the switch may be so proportioned and so positioned that the spring 35 will bear against the abutments 38 or 39,- in the normal or abnormal position as the case may be, to maintain contact. However, in certain cases where it is desired to maintain good contact pressure up to the time of snap over, the holding spring 42 as shown will be advantageously-employed.

It will usually be preferable to mount the movable contact sufficiently loosely on the carrier that it will be free to pivot a limited amount to equaliz the contact pressure on each of the pairs of stationary contacts to compensate in a very simple and inexpensive manner for unavoidable misalignment of the contacts.

While a particular form of the present invention has been shown, it will be apparent that minor changes therein will readily suggest themselves to others skilled in the art without departing from the spirit and scope of the invention. Having thus described the invention, what is claimed as new is:

1. In a snap acting device, a unitary member movable between preselected positions defined by stops, a plurality of over-center snap spring mechanisms comprising transversely defiectable compression elements operative on said movable member for driving the same between said preselected positions, one of said compression elements being movable by said member through a position of unstable equilibrium to hold said member in one of said preselected positions, a second of said compression elements having a lost motion engagement with said member, and means to move said second compression element an initial amount independently of said member through an axis of maximum stress to move said member to one of said preselected positions by hammer blow snap action.

2. The combination recited in claim 1 wherein said means for moving said second compression element is biased in one direction to cause said movable member to normally assume one of said preselected positions.

3. In a snap acting device, an elongated member movable axially between preselected positions and having spaced abutments, a helical overcenter snap spring engageable alternately with the spaced abutments on said movable member, and means for moving said spring in one direction while remaining in engagement with one of said abutments and while said member is in one of said preselected positions until said spring is moved through an axis of maximum stress,

whereupon said spring is caused to snap in the opposite direction through a lost motion space into engagement with the other of said abutments to move said movable member by hammer blow snap action between said preselected positions.

4. In a snap acting device, a longitudinally movable member movable between preselected positions and having spaced abutments formed thereon, an overcenter snap spring system for moving said member between said preselected positions and maintaining it stably in one or the other of said positions, said spring system including a transversely deflectable compression element whose axis of compression is substantially at right angles to the axis of movement of said movable member and engageable alternately with said spaced abutments on said movable member to form a lost motion connection therebetween, a movable operator or moving said compression element independently of movement of said movable member through an unstable position to cause said compression element to move by snap action through said lost motion connection to engage said movable member with a hammer blow to move said movable member between said preselected positions. and means for limiting movement of the operator in both directions.

5. In a snap acting switch. a unitary carrier for a contact movable to and from a stable switching position, a first over-center snap spring engageable with said carrier to maintain it in said stable position, a second overcenter spring directly engaging said carrier. means for moving said second spring inde endently of movement of said carrier through an unstable position of maximum stress to initiate snap action movement of said second spring through a lost motion space to disengage said carrier and engage it in a different place at high velocity to move said carrier and said contact away from said stable position in a hammer-blow snap-action manner.

6. In a snap acting switch, a longitudinally movable carrier for a contact movable between prese ected switching positions and having spaced abutments formed thereon, an overcenter snap spring system for moving said carrier between said preselected positions and maintaining it stable in one or the other of said positions, said spring system including a transversely defiectable compression element whose axis of compression is substantially at right angles to the axis of movement of said movable carrier and engageable alternately with the spaced abutments on said movable carrier to form a lost motion connection therebetween, means for moving said compression element independently of movement of said carrier through an unstable position of maximum compressive stress concurrent with application of force to said carrier to maintain it in one or its said preselected positions to initiate snap action movement of said compression element through said lost motion connection to engage said carrier in a difierent place at high velocity to move said carrier and said contact between said preselected positions in a hammer-blow snap-action manner.

7. In a switch, the combination of an elongated contact carrier movable axially between preselected positions and having spaced abutments formed thereon, a first laterally deflectable compression member secured to said carrier and having an axis of maximum stress and alternate positions of reduced stress, said first compression member in one position of reduced stress maintaining said movable member in one of its preselected positions and in the other position oi reduced stress maintaining the movable member in the other of its preselected positions, a second laterally defiectable compression member for moving said carrier between its preselected positions and for moving the first compression member from one position of reduced stress through its-axis of maximum stress, said second compression member having an axis of maximum stress and alternate positions of reduced stress and being engageable with the carrier through the spaced abutments, and means for moving said second compression member from one position of reduced stress through its axis of maximum stress so that said latter compression member moves relative to said carrier to engage one of the abutments with a snap action to thereby impart a hammer blow to said carrier in its movement between thepreselected positions.

8. In a switch, the combination of a contact carrier movable between preselected positions and having spaced abutments formed thereon, a first laterally defiectable compression member secured to said carrier and having an axis of maximum stress and alternate positions of reduced stress, said first compression member in one position of reduced stress maintaining said movable member in one of its preselected positions and in the other position of reduced stress maintaining the movable member in the other of its preselected positions, a second laterally deflectable compression member for moving said carrier between its preselected positions and for moving the first compression member from one position of reduced stress through its axis of maximum stress, said second compression member having an axis of maximum stress and alternate positions of reduced stress and being engageable with the carrier through the spaced abutments, means for moving said second compression member from one position of reduced stress through its axis of maximum stress so that said latter compression member moves relative to said carrier to engage one of the abutments with a snap action to thereby impart a hammer blow to said carrier in its movement between the preselected positions, and means for limiting movement of said latter means. a

9. In a snap acting switch, the combination of a base, an elongated member movable between opposed positions having an elongated slot at one end forming opposed abutments and an aperture at the opposite end of the member, fixed spaced brackets on opposite sides of said elongated member adjacent said aperture, a spring element extending through said aperture and attached at opposite ends to said brackets, said spring element being biased to maintain said elongated member in either of its opposed positions, a yoke movable relative to said elongated member having arms disposed on opposite sides of said member adjacent said elongated slot, a spring element extending through said slot and supported by said arms, said second spring element being movable relative to said elongated member, and

- means for moving said yoke relative to said elongated member to move the supported ends of the second spring element through an axis of maximum stress whereby said spring engages an end of the elongated slot with a hammer blow in a direction against the hol ng action of the first spring element.

ARTHUR L. RICE.

& REFERENCES crrm The following references are of record in the file of this patent:

France Apr, 14, 1927 

